The world celebrates Earth Hour

March 23, 2013 |compiled from wire photos

Millions of people were expected to switch off their lights for Earth Hour on March 23 in a global effort to raise awareness about climate change that was even to be monitored from space.

NIKOLAY DOYCHINOV/AFP/Getty Images

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Fire acrobats perform in front of the Bulgarian National Theatre, with lights turned off, as part of the Earth Hour in Sofia on March 23, 2013. Millions of people were expected to switch off their lights for Earth Hour on March 23 in a global effort to raise awareness about climate change that was even to be monitored from space.

NIKOLAY DOYCHINOV/AFP/Getty Images

1of15

Fire acrobats perform in front of the Bulgarian National Theatre, with lights turned off, as part of the Earth Hour in Sofia on March 23, 2013. Millions of people were expected to switch off their lights for Earth Hour on March 23 in a global effort to raise awareness about climate change that was even to be monitored from space.